Broadcast BC-7A User manual

Broadcast Equipment
Instructions
BC -7A
Stereo/Dual-Channei
Consolette
MI -11657-A
Commercial Electronic Systems Division/Front and Cooper Streets/Camden, New Jersey, U.S.A. 08102

EQUIPMENT LOST OR DAMAGED IN TRANSIT
When delivering the equipment to you, the truck driver or carrier's
agent will presenta receipt for your signature. Do not sign it until you
have (a) inspected the containers for visible signs of damage and (b)
counted the containers and compared with the amount shown on the
shipping papers. If a shortage or if evidence of damage is noted, insist
that notation to that effect be made on the shipping papers before you sign
them.
Further, after receiving the equipment, unpack it and inspect thoroughly
for concealed damage. If concealed damage is discovered, immediately
notify the carrier, confirming the notification in writing, and secure
an inspection report. This item should be unpacked and inspected for
damage WITHIN 15 DAYS after receipt. Report all shortages and da-
mages to RCA, Commercial Electronic Systems Division- Camden,
New Jersey 08102.
RCA will file all claims for less and damage on this equipment solong
as the inspection report is obtained. Disposition of the damaged item
will be furnished by RCA
FIELD ENGINEERING SERVICE
'RCA Field Engineering Service is available at current rates. Requests
for field engineering service may be addressed to your RCA Broadcast
Field Representative or the RCA Service Company, Incorporated -
Broadcast Service Division - Camden, New Jersey 08102. Telephone
609-963-8000.
WARRANTY ITEMS
l'articular parts and/or equipments covered by warranty are specif-
ically stated as such in the warranty or contract given to the customer
at the time of sale. The warranty orcontract alsostipulates the condi-
tions under which the warranty may be exercised.
To obtain new replacement for such warranty items, contact your local
RCA sales office and please supply Product Identification (including
the Original Invoice Number, MI Number, Type Number, Model Number,
and Serial Number) and Replacement Part Identification (including Stock
Number and Description). Requests for warranty replacements may
be unduly delayed if all this. information is not supplied.
REPLACEMENT PARTS
When ordering replacement parts, please give Stuck or Master Item
(MI) Number, Description, and Symbol of each item ordered.
The part which will be supplied against an order for a replacement
item may not be an exact duplicate of the original part. However, it
will be a satisfactory replacement differing only in minor mechanical
or electrical characteristics. Such differences will in no way impair
the operation of the equipment.
Emergency
For emergency services after working hours, contact RCA Parts and
Accessories, Telephone [phone].
LOCATION ORDERING INSTRUCTIONS
Continental United States, including
Alaska and Hawaii Replacement Parts bearing a STOCK NUMBER should be ordered from RCA Parts and Accessories-
2000 Clements Bridge Road - Deptford, New Jersey 080%.
Replacement Parts bearing a MASTER ITEM (MI) NUMBER should be ordered from RCA.
Commercial Electronic Systems Division - Attention Commercial Service - Camden, NewJersey
08102 or your nearest RCA Regional Office.
Replacement Parts with NO STOCK or MASTER ITEM (MI) NUMBER are standard components.
They are not stocked by RCA and should be obtained from your local electronics distributor.
Dominion of Canada Order from your local RCA Sales Representative or his office or from: RCA Victor Company
Limited, 1001 Lenoir Street, Montreal, Quebec.
Outside of Continental United States.
Alaska, Hawaii, and the Dominion of
Canada
Order from your local RCA Sales Representative or from: RCA International Division, Clark,
New Jersey - U. S. A. - Wire: RADIOINTER
Emergency: Cable RADIOPARTS, DEPTFORD, N. J.
RETURN OF ELECTRON TUBES
If for any reason it is desired to return tubes, please return them
throughyour local RCA tubedistributor, RCA Victor Company Limited,
or RCA International Division, depending on your location.
Please do not return tubes directly to RCA without authorization and
shipping instructions.
It is important that complete information regarding each tube (including
type, serial number, hours of service and reason for its return) be
given. When tubes are returned, they should be shipped to the address
specified on the Return Au thormation form. A copy of the Return Author-
izationand alsoa Service Report for each tube should be packed with the
tubes.
LOCATION ORDERING INSTRUCTIONS
Continental United States, including
Alaska and Hawaii Local RCA Tube Distributor.
Dominion of Canada Order from your local RCA Sales Representative or his office or from: RCA Victor Company
Limited. 1001 Lenoir Street. Montreal, Quebec.
Outside of Continental United States.
Alaska, Hawaii, and the Dominion of
Canada
Local RCA Tube Distributor or from: RCA International Division. Clark, New Jersey, U.S.A. ,
Wire. RAMONTER
Emergency. Cable RAMPARTS, DEPTFORD, N.J.
RTE -M4

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2
TECHNICAL DATA
Mixers
10 2 db per step 600 -ohm attenuators. Includes dual sec-
tion "synchronized" attenuators in positions 5 thru
8 and cue tap on mixers 5 thru 10 (cue tap on mixer
5 not factory connected to cue bus; tap may be jump-
ered to cue bus in field if desired). Plug-in units
provide choice of lo -level or hi -level, balanced or
unbalanced input to any or all mixers.
Inputs
31 inputs available on switches to mixers. This includes
12 factory wired dual -channel stereo inputs to 4
dual -channel stereo mixers. Switch contacts are pro-
vided to wire companion right channel of any or
all input switches. Any or all single -mixers can be
directly replaced by stereo mixers. All mixer delega-
gation switches are pre -wired for stereo -mixers.
Three of the inputs are switchable to either mixer
9 or 10 for added flexability. Four remote lines are
switchable to program -cue, intercom or mixer 10.
4 auxiliary inputs available on switches to monitor
amplifiers (2 for each monitor).
Amplifiers and Power Supply
(normally furnished for stereo operation)
plug-in transistor preamplifiers plus provision for 5
additional preamps (choice of either plug-in pre -
amp, hi -level isolation unit, or jumper plug for all
10 mixers).
2 plug-in transistor program amplifiers.
2 plug-in transistor monitor amplifiers (consolette may
be operated with only one monitor amplifier for
mono.).
Iplug-in cue/intercom amplifier.
Iplug-in power supply.
6
Outputs
2 program lines (channels may feed either or both
lines).
2 external monitor lines (one for each program
channel).
10 speaker lines (each of 5 locations may monitor in
stereo, each monitor line wired through on -air inter-
lock muting relays).
program cue to 4 remotes.
5 intercom lines (4 wired thru on -air interlock relays,
Ispare).
Source Impedance
Microphones:
37.5/150/600 ohms
Net, Aux and Remote Lines:
600/150* ohms
Recorded Inputs (turntable, tape film)
.600 ohms unbalanced (if jumper plug is used)
600/150* ohms (if plug-in isolation unit is used)
*Hi -level isolation unit has transformer tap for 150 -ohm;
input pad resistors can be easily replaced for 150 -ohm
operation.
Load Impedance
Line600 ohms
Speaker
16 ohms*
*(Use external matching transformer for speaker of lower
impedance.)
Headphone
High impedance
Output Levels
Program channel
+18 dbm (+8 vu) after 6 db isolation pad
Monitor amplifier
+40 dbm (10 watts; 2 watts
loads)
Program cue to remote
+18 dbm (+8 vu)
Program channel external monitor terminals
-6 dbm (-16 vu)
Input Levels
MicbroPlsone
Normal:
to each of 5 speaker
-60 vu program level (-50 dbm con-
tinuous sine wave test input) to produce
standard output (Note 1) of consolette,
with normal operating position of mixer
and master attenuators (Note 2).
Maximum: -32 vu program level ( - 22 dbm con-
tinuous sine wave test signal) maximum
input to preamplifier.
Recorded Inputs (turntable, tape, etc.)
Normal: -20 vu program level ( -10 dbm sine
wave test signal) to produce standard
output (Note 1) with normal operating
position of mixer and master attenuators
(Note 2).
Net, Any. & Remote Lines
Normal: 0 vu program levet (+ 10 dbm sine wave
test signal) input to 20 db tap of tapped
fixed attenuator. Input may be connected
to taps at 0, IO, 20, 30, or 40 db to
produce standard output (Note 1) with
normal operating position of mixer and
master attenuators (Note 2).
Auxiliary External Input to Monitor Amplifier
Normal: 20 vu (-- 10 dbm) for same operating
position of the monitor gain control as
used for monitoring program line.

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TECHNICAL DATA (Continued)
Gain
Microphone input to program line
106 db
(preamp can be strapped to increase total maximum
gain to 112 db)
Recorded Inputs (turntable, tape, etc.) to program line
max 66 db
Network, Auxiliary and Remote lines to program lines
max 66 db
Microphone input to speaker line
max 127 db (with 40 db preamp strapping)
max 133 db (with 46 db preamp strapping)
Auxiliary external -input -to -monitor to speaker line
max 57 db
Signal -to -Noise Ratio
Microphone to Program Line
Normal operating position of operating controls
(Note 2)
(68 db gain; +18 dbm output)
Notes
68 db
I. Standard Output Level is vu program level (+ 18
dbm steady state sine wave test signal) (Consolette
VU meters read "0- on VI: scale [100%) for +8
vu output of consolette with program material, and
will be pinned for 4-18 dbm output-this is stand-
ard practice and in no way damages meter during
test.)
2. Normal operating position of Mixer and Master at-
tenuators is "13- for mixer (14 (lb reserve gain)
and "8" for master (2.1 dh reserve gain): a total of
38 db reserve gain.
Frequency Response
program channels ± 1.5 db 30 to 15,000 cps;
monitor channels -± 2 db 30 to 15,000 cps
Distortion
Program Channel:
less than .5% 50-15,000 cps
less than .75% 30 cps
Monitor Amplifier:
less than 1% 50-15,000 cps
Dimensions
391/4" wide, 121/2" high, 20" deep.
Weight
MI -11657
Consolette housing (less all plug-in units) 100 lbs
ES -11157 -AS Consolette with normal
complement of plug-in units for stereo
programming. 160 lbs
ES -11157-A Consolette with normal
complement of plug-in units for monaural
programming. 115 lbs
FinishMain control panel-anodised brushed aluminum
(lousing-shadow blue textured vinyl.
Power Required
115 or 230v 501,0 cps Normal: 55-65 watts
Maximum: Approx. 120 watts
Stand by: 55 watts

4
Figure P. Type BC -7A Stereo/Dual Channel Consolette MI -11657-A

5
Introductory Description
The BC -7A Stereo/Dual-Channel Consolette is a
self-contained, audio system of broadcast quality, for
stereo or monaural programming. It was designed
primarily for radio and TV studio use, but its features
are such that it may be found well adapted to more
varied uses, wherever a high quality sound control
console is needed. It has mixing, switching, and moni-
toring facilities, plus cue and intercom provisions
which employ an independent amplifier with auto-
matic gain control. It uses low impedance mixing
circuits and dependable plug-in transistor amplifiers
and power supply.
The consolette normally accommodates inputs from
microphones, turntables, magnetic tape and remote
lines. Its control circuits provide facilities for operat-
ing warning light relays, muting studio monitor and
intercom speakers, and automatically starting recorded -
input equipment such as turntables, tape reel and
cartridge equipment, projectors, etc.
The consolette basically provides two independent
high gain program amplifier channels, each receiving
a signal from a separate input mixer bus. Each pro-
gram amplifier has an associated master gain control,
VU meter and line pad and is capable of producing
line level output. Two program output lines are pro-
vided. Each output line has a three -position selector
switch to provide selection of signal from either the
left or right program amplifier and a center off posi-
tion to terminate the line.
Ten variable attenuators (mixers or faders) provide
facilities for simultaneous mixing of up to ten input
channels. Above the mixer knobs are source selector
lever switches with colored handles and mixer delega-
tion lever switches with black handles. Switches asso-
ciated with individual mixers are located immediately
above the particular mixer with which they are asso-
ciated. The "black" mixer delegation switches provide
assignment of the output of each mixer to either the
left channel mixer bus or the right channel mixer bus.
Within the consolette a receptacle is provided for each
mixer to accept various plug-in units:
(1) A preamplifier for use with microphone sources,
(2) A high-level isolation unit with strap adjustable
pad for line level sources.
(3) A jumper plug for direct input to the mixer.
Flexibility is thus achieved such that any or all mixers
can accommodate a wide variety of sources.
DESCRIPTION
Facilities are provided for two independent monitor
amplifiers, each with a 2 db per step attenuator and a
4 position input selector switch by means of which
each monitor may be connected to the left or right
program amplifier or auxiliary sources. For stereo op-
eration, the two monitor gain controls are electrically
ganged together for simultaneous balanced control
from a single knob. For monaural operation, the sec-
ond monitor amplifier may be used for audition or to
preview" the signal or may be omitted or added
later if desired. The combination of units selected is
dependent upon individual requirements.
A combination microphone/loudspeaker is located
in the center of the main control panel. A guide/
receptacle assembly, located behind the panel on the
lower deck, accepts a separate amplifier with AGC
for two -was' communication with studio intercom sta-
tions (MI -11452) and communication with remote
lines. A 12 -position selector switch on the main con-
trol panel provides positions to use the intercom am-
plifier to monitor the mixer cue -bus and network line,
independent of other monitor facilities, as well as
serve the intercom function.
A mode selector switch is provided to set up the
consolette for Stereo -Programming or Dual -Channel
Monaural -Programming with two independent chan-
nels. With the Mode switch in the Stereo position the
left and right channel, master gain controls are elec-
trically ganged for simultaneous control from a single
knob. Similarly, the left and right channel monitor
controls are connected for simultaneous balanced con-
trol from a single knob. A third position of the mode
selector switch (labeled PARALLEL) ties the two
program amplifiers together after the master gain
controls. Thus each master becomes a submaster for
deluxe monaural operation.
Flexibility and simplicity are outstanding features
of the BC -7A consolette. Interchangeable plug-in units
and liberal use of jumper terminals provide a wide
choice of inputs for each mixer position, and easy
access to key parts of the circuit. Functional grouping
and color coding of controls, and particular attention
to labeling, create an uncluttered panel and minimize
operator error. Permanent panel designations are
etched in black whereas controls with designations
which are most dependent on individual needs are
provided with uniform panel depressions provided to
accept a wide assortment of pressure sensitive metal
labels supplied with each unit. The labels give a neat,
permanent appearance to the consolette yet provide
concise accurate descriptive labeling which can be
changed when necessary.

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Detailed Description
Refer to the fold -out sheet at the back of this book
immediately preceding the schematic diagram. When
this sheet is folded out, the functional diagram (fig-
ure 25) and a view of the control panels, in which all
controls are identified (figure 24) extend beyond the
other pages of this book for reference while reading
the explanations throughout this book.
Mixers, Selector and Delegation Switches
There are ten attenuators (often referred to as
mixers or faders) arranged across the lower portion
of the control panel in two groups of five equally
spaced knobs. In a typical installation the left group
of five mixers (1, 2, 3, 4 and 5) with black knobs may
normally be used for microphone inputs. The three
mixers to the right (mixers 6, 7 and 8) with blue
knobs may normally be used for recorded inputs
(turntable, tape, etc.). Mixer 9, with the green knob,
would ordinarily be used for NETWORK and aux-
iliary inputs and mixer 10, with the red knob, would
be used for remote inputs.
Above the mixer attenuator knobs are SOURCE
SELECTOR SWITCHES, distinguished by colored
handles, and MIXER DELEGATION SWITCHES,
all of which have black handles. All source selector
switches and mixer delegation switches are located
immediately above the mixers with which they are
associated, to minimize operator error.
The output of each mixer may be delegated to the
left channel mixer bus (program amplifier 1) by
throwing its black MIXER DELEGATION SWITCH
to the left, or it may be delegated to the right channel
mixer bus (program amplifier 2) by throwing the
switch to the right. The center position is the off
position.
Note that the left position of the mixer delegation
switches located above mixers 5, 6, 7 and 8 (S-25,
S-26, S-27 and S-28) has the designation STEREO in
addition to the normal designation CH -1. This indi-
cates that when the consolette is set up for stereo
operation (see discussion under MODE switch, p. 8)
and one of these mixer delegation switches is in the
CH -1 position, the output of the left channel sec-
STEREO
tion of the mixer is delegated to the left channel
mixer bus and the output of the right channel section
of the mixer is simultaneously delegated to the right
channel mixer bus. The right position of these
switches is not used for stereo operation. As may be
seen on the audio functional diagram the right chan-
nel section of the dual section stereo mixer is termin-
ated when the corresponding mixer delegation switch
is in the CH -2 position.
The source selector switches for mixer 1 through 8
provide selection of 3 pre -wired sources to each mixer.
In a typical installation, throwing mixer 1 source
selector switch (S-1) to the left position (normally
labeled studio A) would connect microphone number
Iof studio A to mixer 1through its plug-in pre-
amplifier. In a similar manner, microphones 2, 3, 4
and 5 of studio A could be connected to correspond-
ing mixers 2, 3, 4 and 5 by throwing source selector
switches S-2, S-3, S-4 and S-5 to the left position. The
left position of each of the 5 source selector switches
would thus be labeled stucho A. The center position
of source selector switches S-1, S-2, S-3 and S-4 would
normally be labeled studio B and throwing these 4
switches to the center position would connect the 4
"microphones in studio B to the corresponding mixers.
In a similar manner the right hand position of these
switches could be used for 4 microphones in studio C.
The center position of mixer 5 source selector switch
(S-5) would ordinarily be used for the announce
booth microphone and the right hand position would
normally be used for the control room microphone.
Source selector switches S-1, S-2, S-3 and S-4 all have
blue handles. Source selector switches S-5, S-6, S-7 and
S-8 all have red handles. The red handles (same color
as mode switch handle) indicate that the mixers below
these switches all hare double section stereo attenua-
tors. The mixer 5 position is unique, in that it norm-
ally has two preamplifiers arranged such that for
stereo programming, the input selected supplies equal
signal to both left channel and right channel sections
of the attenuator for balanced override of both chan-
nels, without upsetting the stereo relation of any
stereo program material coming in on other mixers.
The three source selector switches with red handles,
above mixers 6, 7 and 8 (S-6, 5-7 and S-8) to the right
of the center of the panel, are normally used for turn-
tables, reel tape, cartridge tape, or projector inputs.
Here again, the red handles indicate dual section
stereo attenuators, which for stereo programming
simultaneously adjust the level of both right and left
channels. For monaural programming the right chan-
nel section of each stereo attenuator is terminated.
For additional flexibility, three inputs are provided
with switching facilities for optional assignment to
either mixer 9 or mixer 10. Above mixer 9 is a group
of three vertical travel switches with green handles.
Each switch controls the delegation of a single source.
For example, throwing the left hand green handle

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(switch S-9), normally labeled NET, to the up posi-
tion (labeled MIX 9) connects the network line to
mixer 9. The center position is an off position. Throw-
ing the handle to the down position (labeled MIX
10) puts the network on mixer 10. The two adjacent
switches with green handles to the right (S-10 and
S-11) may normally be labeled AUX-1 and AUX-2
and are used for similar flexible input to either mixer
9 or mixer 10.
Above mixer 10 is a group of 4 vertical travel,
three -position, lever switches with blue handles (S-12,
S-13, S-14 and S-15). These switches are normally
labeled REMOTE 1, REMOTE 2, REMOTE 3 and
REMOTE 4. Throwing a remote switch to the up
position (labeled PGM-CUE) sends program cue to
that remote location. The cue signal is obtained from
the output of monitor amplifier 1 and fed through a
suitable attenuator, through the remote line, to the
operator at the remote location. (If desired, monitor
amplifier 2 can be used for the PGM-CUE feed in-
stead of monitor amplifier 1 by changing the position
of the jumper wires on TB -2, terminals 1/2, 7/8, and
13/14.) Throwing the switch to the down position
(labeled MIX -10) connects the remote line to mixer
10. In the center position (labeled T.B. for talk back)
the remote line is available for two-way communica-
tion between the consolette and the remote location
using the cue/intercom amplifier.
Under typical operating conditions two-way com-
munication between personnel in the control room
and personnel at the remote location, necessary for
setup of the remote pickup, can be carried on with
the remote switch in the center position. Just before
air time the remote switch can be thrown up to give
the remote personnel cue from the on air program.
Then at the desired time the remote can be cut in by
throwing the remote switch down, connecting it to
mixer 10 which has been preset at the desired gain.
Cue/intercom
The CUE/INTERCOM selector switch (S-61) is
located in the center of the main control panel. It is
a12 -position rotary switch and is associated with
the combination microphone/loudspeaker immediately
above the selector switch, and the PUSH -TO -TALK
switch (S-62) and GAIN control (AT -31) below the
selector switch.
The four positions to the left of center, labeled
REM 1, REM 2, REM 3 and REM 4 permit two-way
communication with any one of the remote lines (pro-
vided they are not connected to mixer 10 or the
program cue line). In the override position all remote
lines can be monitored simultaneously.
The four positions to the right of center, labeled
AN BTH, STU A, STU B and STU C are for two-
way communication with individual announce booth
and studio intercom stations. A spare position is also
provided. The outgoing line from the spare intercom
position is not wired through interlock muting relays.
The top position of the CUE/INTERCOM selector
switch, labeled CUE, is used to monitor the mixer
cue bus and.the bottom position, labeled NET, is used
to monitor the network line.
The plug-in cue/intercom amplifier employs AGC
to maintain the output level of the amplifier essen-
tially independent of input level over about a 25db
range; therefore, -the control below the PUSH -TO-
TALK switch, labeled GAIN, since it follows the
amplifier , could more accurately be described as an
"output level control." It enables the console operator
to establish, essentially independent of input, the level
at which he wishes to listen to intercom stations and
remote lines, as well as cue up records, tape and net-
work.
Alonitors
In addition to the CUE/INTERCOM amplifier,
facilities are provided for two monitor amplifiers. For
stereo operation monitor amplifier 1 is used to moni-
tor the left channel (Channel -1) mixer bus and moni-
tor amplifier 2 is used to monitor the right channel
(Channel -2) mixer bus. For monaural operation,
monitor amplifier 1 can be used to monitor the pro-
gram bus and monitor 2 can be used to monitor the
audition bus or "preview" the signal. The left monitor
amplifier MON AMP -1 and its controls are located
on the left side of the console as viewed from the
operating position, and the right monitor amplifier
MON AMP -2 and its controls are located on the right
side of the console.
Immediately to the left of the intercom -grill is a
red control knob labeled Master -1 (AT -21), which
controls the gain of the left channel program ampli-
fier (PGM AMP -1) for monaural operation and con-
trols the gain of both program amplifiers for stereo
operation (as determined by the MODE SWITCH
S-43, see p. 8). Immediately to the right of the
intercom -grill is a red control knob labeled Master -2
(AT -22) which controls the gain of the right channel
program amplifier 2 for monaural operation, and is
disconnected from the circuit for stereo operation. For
dual channel monaural operation program amplifier 1
may be used for a program channel and program
amplifier 2 may be used for audition. Both master
gain controls are 20 step, 2 db per step, 40 db total

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8
attenuators. The omission of an off position for these
controls is an operating aid to prevent a completely
dead program if the control is accidentally turned or
left in the extreme counterclockwise position.
The attenuator with the green knob (labeled MON-
1) to the left of the intercom grill is a dual section,
2 db per step attenuator (AT -11), which controls the
gain of only monitor amplifier I for monaural opera-
tion and the gain of both monitor amplifiers for
stereo operation. The attenuator with the green knob
(labeled MON-2) to the right of the intercom grill
is a single section 2 db per step attenuator (AT -12)
which controls the gain of monitor amplifier 2 for
monaural operation, and is disconnected from the cir-
cuit for stereo operation.
Immediately adjacent to each monitor amplifier
gain control is located a four -position rotary monitor-
input -selector switch. Each switch provides selection
of Channel -1 (left channel), Channel -2 (right chan-
nel) and two auxiliary inputs. The auxiliary inputs are
brought to the main terminal block (TB -2 45/46;
39/40; 33/34; 27/28) so that external sources can he
monitored as desired. Thus a total of four auxiliary
monitor inputs are available.
An input level of 20%11 at the auxiliary input ter-
minals of the monitor input selector switch will allow
the same operating position of the monitor gain con-
trol as used for monitoring of the outgoing lines.
Auxiliary Switches
The two vertical -travel three -position lever switches
in the upper left section of the main control panel
are unwired auxiliary switches. The switch contacts
provided are two form D contacts (make before
break) each side of center position. These switches are
provided for any special needs of individual stations.
Line Out Switches
In the center of the top panel are two lever switches
with black handles. The top switch is labeled LINE I
and the switch below it is labeled LINE 2. These are
the selector switches for the two outgoing program
lines from the consolette. Throwing LINE 1 switch
(S-41) to the left position (labeled CH -1) connects
outgoing line 1 to the output of the left channel pro-
gram amplifier (pgm amp -1) through a 6 db isola-
tion pad. Similarly, throwing it to the right position
(labeled CH -2) connects it to the right channel pro-
gram amplifier (pgm amp -2). The center position is
an off positioh which terminates the outgoing line and
back -loads the 6 db isolation/dividing network. LINE
2 switch (S-42) operates in a similar manner. Nor-
mally, for stereo operation Line 1 would be used for
the left channel signal by throwing S-41 to the left
position (labeled CH -I) ar.d Line 2 would be used
for the right channel signal by throwing S-42 to the
right position (labeled CH -2).
Mode Switch
The lever switch with the red handle located in the
center of the upper panel is a MODE selector switch
(S-43). Throwing the MODE switch to the left posi-
tion, labeled STEREO, sets up the console for stereo
operation; channel Iis assigned to the left channel
and channel 2 is assigned to the right channel. The
right channel half of stereo mixers 5, 6, 7 and 8
are connected to the corresponding source selector
switches and the channel I and channel 2 master gain
controls are electrically ganged so that both program
amplifier channel gains are equal and are controlled
by the Master -1 gain control. In a like manner the
channel 1and channel 2 monitor gain controls are
ganged and are both controlled by the MON 1 gain
control.
When the MODE switch is in the center position
labeled PARALLEL the two program amplifiers are
internally connected in parallel after the gain control,
thus effectively making master gain control 1, sub -
master 1and master gain control 2, submaster 2.
Throwing the mode selector switch to the right posi-
tion labeled DUAL provides two independent chan-
nels, thus dual channel operation.
Monitor Phones
The 12 -position rotary switch on the extreme left
of the top panel (S-63) is a monitor phones selector
SNN itch which provides a roving monitor -phones facil-
ity to monitor key points throughout the console inde-
pendent of all other amplifiers. Remote lines 1, 2, 3
and 4; channels I and 2; lines 1 and 2; cue bus; and
network line are available, together with two spare
positions. The monitor phones jack for this switch is
located at the lower left corner of the main front
panel. It is the top jack (J-3) labeled S\X' (for switch)
of the pair of jacks labeled PHONES. The bottom
jack of this pair (J-4) labeled AMP (for amplifier)
connects to the CUE/INTERCOM amplifier. Normal -
through contacts are provided so that inserting a
phone plug lifts off the loudspeaker of the cue/
intercom and substitutes the monitor phones ahead of
the control room intercom speaker muting relay. The
combination microphone/speaker still functions as
amicrophone for intercom use when the phone
plug is inserted. The pair of phone jacks located
at the lower right corner of the main front panel
provide direct monitoring of the two outgoing lines
L-1 (J-1) and L-2 (J-2).

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